<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<script type="text/javascript" src="js/jquery-1.11.3.min.js"></script>
<body>
	<select id="one">
		<option class="A1">1</option>
		<option class="A2">2</option>
		<option class="A3">3</option>
		<option class="A4">4</option>
	</select>
	<select id="two">
		<option id="A1">11</option>
		<option id="A2">22</option>
		<option id="A3">33</option>
		<option id="A4">44</option>
	</select>
</body>
<script type="text/javascript">
	$("#one").change(function(){
		var cla=$("#one option:selected").attr("class"); //获取select当前值得选择器class
		$("#two").val($("#"+cla).val())
	})
	$("#two").change(function(){
		var id=$("#two option:selected").attr("id"); //获取select当前值得选择器id
		$("#one").val($("."+id).val())
	})
</script>
</html>